Contributed by Peter W. Schutz, MD, PhD1; Christopher R. Honey, MD, DPhil, FRCS2; Stephen Yip, MD, PhD, FRCPC1
Divisions of Neuropathology1 and Neurosurgery2, Vancouver General Hospital, University of British Columbia - Vancouver, British Columbia, Canada.
A previously healthy, 35-year-old man presented with a four-week history of painful swelling on his right forehead. CT imaging showed a solitary, 1 cm osteolytic lesion within the diploic space of the right frontal bone, involving the inner and outer tables (Figure 1). On MRI, the lesion was heterogeneously enhancing and extended into subgaleal tissue and epidural space. It was resected and the patient was discharged in good condition.
6 months after his surgery, pain and swelling near the area of the previous resection recurred. CT showed a bland resection site (Figure 2) and a new lytic lesion in an adjacent sagittal plane, about 2 cm removed from the initial resection site (Figure 3). The second lesion was surgically removed.
H&E stained sections of the first lesion showed sheets of discohesive, mildly pleomorphic cells with ovoid to bean-shaped nuclei, frequent nuclear indentation and lobulation and occasional nuclear grooves, fine chromatin, thin nuclear membranes and inconspicuous nucleoli. There was a pronounced mixed inflammatory infiltrate present, composed predominantly of eosinophils along with lymphocytes, neutrophils, and macrophages (Figure 4). Atypia and mitotic activity were minimal. Cells were strongly positive for CD1a (Figure 5) and S-100 (Figure 6). The specimen was received in fragments and relationship to bone could not be evaluated. The second resection showed similar histology, nuclear detail (Figure 7), and immunoprofile. What is the diagnosis?